It has been found that when nucleophilic reagents are reacted with isatoic anhydride (R. P. Steiger, E. M. Miller, J. Org. Chem. 24, 1214 (1953); ibid, 18, 1427 (1953)), the reaction may proceed along two lines: ##STR1##
Thus, for example, when the reaction is carried out using aliphatic hydroxyl compounds, the reaction path along (A) leads to an anthranilic acid derivative and along (B) to a urethane-o-benzoic acid. The ratios in which the two reaction products are obtained depend to a great extent on the reaction conditions, particularly on the nature of the nucleophilic reagent, the catalyst, the reaction temperature, and the like.
The presence of free carboxyl groups in the products of the process often interferes severely with the quality of the polymers subsequently produced from these product mixtures by further reactions. Apart from any side reactions which the carboxyl groups may undergo, such as the reaction with isocyanates, the carboxyl groups have the effect of substantially reducing the resistance of the polymers to hydrolysis. It is therefore desirable to keep the number of carboxyl groups in the reaction products of polyols or polythiols and isatoic acid anhydride as low as possible.
In U.S. Pat. No. 3,808,250, a process is described wherein compounds containing OH and/or SH groups and having molecular weights of from 600 to 10,000 are reacted with substantially equivalent quantities of isatoic acid anhydride in the presence of a base. It was found, however, that in this process, the proportion of reaction mixture undergoing the above-described side reaction (B) is relatively high. As may be seen from the following Table 1, the reaction of polyethers with equivalent quantities of isatoic acid anhydride at about 110.degree. C. in the presence of various catalysts yields products, in which the proportion of amine groups to acid groups (hereinafter referred to as A/S ratio) is in no case higher than 8:1.
Table 1 __________________________________________________________________________ Polyether Catalyst A/S ratio __________________________________________________________________________ linear copolymer of propylene oxide and permethylated diethylene 8 : 1 ethylene oxide; OH number 56, primary OH triamine groups copolymer of propylene oxide and ethylene permethylated diethylene 8 : 1 oxide; OH number 56, trifunctional, triamine primary OH groups copolymer of propylene oxide and ethylene dimethylbenzylamine/tetra- 3 : 1 oxide; OH number 41; trifunctional, methylguanidine (10 : 1) secondary OH groups polypropylene oxide started on trimethylol dimethylbenzylamine/tetra- 5 : 1 propane; OH number 870 methylguanidine (10 : 1) mixture of linear polypropylene oxide -- 5 : 1 (OH number 56), triethanolamine and N-methyl-diethanolamine (100 : 4 : 6 parts, by weight) __________________________________________________________________________
In U.S. Pat. No. 3,929,863, a proces is described wherein compounds containing OH and/or SH groups and having molecular weights of from 76 to 599 are reacted with from about 0.8 to 1.2 equivalents of isatoic acid anhydride in the presence of a base. Because of their relatively low molecular weight, the compounds described therein are excellent chain extenders for polyurethane resins.